1. Field of the Invention
The present invention is directed to a technology related to temporarily storing of read image data.
2. Description of the Related Art
Image reading apparatuses that can read images of two sides of an original simultaneously are known in the art. Such image reading apparatuses typically have a memory and temporarily store read image data in the memory before outputting the image data. Such image reading apparatuses have been disclosed in, for example, Japanese Patent Application Laid-open No. 2006-295546, Japanese Patent Application Laid-open No. 2007-081687, and Japanese Patent Application Laid-open No. 2005-242917.
Japanese Patent Application Laid-open No. 2006-295546 teaches using a read-page memory area for storing therein scanned image data of an original and an output-page memory area for storing therein image data to be output. When images of two sides of a two-sided original are to be read, image data of a first side of the original is stored in the read-page memory area whereas image data of a second side is stored in the output-page memory area.
The technology disclosed in Japanese Patent Application Laid-open No. 2007-081687 is directed to an image reading apparatus that is connected to an external apparatus and is capable of reading an image of a first side of an original and that of a second side at one time. The image reading apparatus includes an image sensor, an analog-digital (A/D) converter, an image processing unit, a parameter setting unit, and a communication unit. Images acquired by reading two sides of a two-sided original are converted into electric image signals by the image sensor. The electric image signals are converted into digital signals by the A/D converter, and then subjected to digital signal processing by the image processing unit. The processed digital image data is sent to the external apparatus by the communication unit. When reading images of two sides of an original at one time, an image of a first side of the original and that of a second side are read differently according to corresponding reading-related parameters that have been determined by a user on a side-by-side basis in advance.
The technology disclosed in Japanese Patent Application Laid-open No. 2005-242917 is directed to an image reading apparatus that includes a storage device. The storage device includes a primary storage unit for temporarily storing therein image data of at least one image and a secondary storage unit for storing therein the image data temporarily stored in the primary storage unit. The image reading apparatus is connectable to a two-sided original reading apparatus that is capable of reading an image of a first side of a two-sided original and that of a second side simultaneously. The image reading apparatus includes a data transfer unit and a data-transfer-rate determining unit. The data transfer unit is capable of transferring image data of the two images, i.e., the image of the first side and that of the second side, substantially simultaneously to the storage device. The data-transfer-rate determining unit determines a transfer rate for the image data of the first side and a transfer rate for the image data of the second side. When transferring these two sets of the image data acquired by the two-sided original reading apparatus to the storage device, the image data are transferred at the transfer rates determined by the data-transfer-rate determining unit.
As disclosed in Japanese Patent Application Laid-open No. 2006-295546, a typical image reading apparatus capable of reading images of two sides of a two-sided original includes a memory for temporarily storing image data therein for a reading mechanism (scanner). Even when images of two sides of an original are read by the image reading apparatus simultaneously to acquire image data of the two images, it is necessary to transfer the image data on a side-by-side basis to a controller. When the image data is to be subjected to image processing, the image processing is also performed on the image data on a side-by-side basis. To adjust timing related to the transfer or the image processing, system control of temporarily storing the image data in the memory or the like is performed. With the method disclosed in Japanese Patent Application Laid-open No. 2006-295546, even when an image of an original that is longer than a predetermined size is read and image data, which is therefore large in size, is acquired, all the image data is temporarily stored in such a memory of the scanner. After all the image data has been stored in the memory, the image data is transferred to the controller. If the size of the image data is larger than the capacity of the memory, the image data will be damaged. One approach could be to use a sufficiently large memory; however, a larger memory is disadvantageously expensive.